Solution processible poly(aniline) via doping with diesters of sulfosuccinic acid M. Zagorska a,* , I. Kulszewicz-Bajer a , O. Blet a , P. Zawirska a , B. Dufour b , P. Rannou b , A. Pron b a Faculty of Chemistry, Warsaw University of Technology, Noakowskiego 3, 00-664 Warsaw, Poland b Laboratoire de Physique des Me ´taux Synthe ´tiques, UMR5819-SPrAM (CEA-CNRS-Univ.J.Fourier-Grenoble I), DRFMC, CEA-Grenoble, 17 Rue des Martyrs, 38054 Grenoble Cedex 9, France Received 22 August 2002; received in revised form 10 October 2002; accepted 18 November 2002 Abstract We demonstrate that similarly as in the case of poly(pyrrole), diesters of sulfosuccinic acid containing alkyl or alkoxy substituents can serve as dopants inducing solution processibility of poly(aniline) (PANI). Free-standing films of PANI doped with sulfosuccinates, cast from 2,2 0 - dichloroacetic acid, show excellent thermal stability and electrical conductivity exceeding 100 S cm 1 which in addition is metallic in character down to 230 K. # 2003 Elsevier Science B.V. All rights reserved. Keywords: Poly(aniline); Diesters of sulfosuccinic acid; Solubility; Electrical conductivity 1. Introduction p-Conjugated polymers are extremely interesting materi- als which can be used not only as semiconductor compo- nents of so-called ‘‘plastic electronics’’ but also as organic conductors of a new generation. Unfortunately, they are rather difficult to process either in their undoped (semicon- ducting) state or in the doped (conducting) state. For this reason, in the last two decades, significant research effort has been undertaken with the goal to improve the processibility of these materials. Classical procedures used in polymer chemistry for inducing the solubilization of stiff backbone polymers consist of branching flexible side-chains (alkyl, alkoxy, etc.) to the main chain. In the case of conjugated polymers, such procedure was initially applied with success to poly(thiophene) [1] and more recently to poly(p-pheny- lenevinylene) [2] and poly(pyrrole) [3]. Unfortunately, func- tionalized conjugated polymers easily processible in the undoped state frequently become more difficult to process after doping. Moreover branching of solubility-inducing groups to the main chain has, in many cases, a negative effect on their conductivity in the doped state. For this reason in early 1990s of the past century, a new procedure for solution processing of unsubstituted conjugated polymers was developed which consists of introducing solubilizing groups as inherent parts of the dopant [4]. In this case polymers, intractable in the undoped state, became solution or thermally processible after doping. This approach some- times called ‘‘counter-ion induced processibility’’ was initially used with success in many systems including poly(aniline) (PANI) [5,6] and poly(pyrrole) [7]. In the case of poly(pyrrole), anions originated from diesters of sulfosuccinic acid (DESSA) turned out to be extremely good dopants converting this polymer into a processible conductor [8]. In particular, it was demonstrated that chemical polymerization of pyrrole in the presence of sodium salt of di-2-ethylhexyl ester of sulfosuccinic acid (abbreviated as Na þ (DEHESSA)  ) results in (DEHESSA)  doped poly(pyrrole) which is soluble in a variety of solvents and upon casting gives reasonably conductive free-standing films with conductivity of the order of few S cm 1 . Inspired by this discovery we have decided to test DESSA as dopants of PANI. One must note here that these molecules in their acid form are sufficiently strong acids to dope PANI via protonation reaction. To our knowledge no acid–base doping of PANI by sulfosuccinates has been reported to date. We have therefore studied the properties of PANI- sulfosuccinates systems focusing on their processibility, spectroscopic and electrical transport properties. Synthetic Metals 138 (2003) 543–548 * Corresponding author. Tel.: þ48-22-660-5584; fax: þ48-22-628-2741. E-mail address: zagorska@chemix.ch.pw.edu.pl (M. Zagorska). 0379-6779/03/$ – see front matter # 2003 Elsevier Science B.V. All rights reserved. doi:10.1016/S0379-6779(02)01248-1